My primary hiking pal and I initially made the decision to go with the Sweetwater System (now MSR Sweetwater) because the filter itself uses a "barn pump" motion rather than a "bicycle pump" motion. My hiking partner was having tendonitis issues with her wrists and she thought it would be better for her to use this one. This was 12 years ago and we have never looked back.
You NEED to use a filter for water in the backcountry (or from any natural source) for purification. The main issues, other than the normal bacteria are Giardia (“beaver fever”) and cryptosporidium. Both of these organisms will cause severe diarrhea which can last for weeks, and in some cases become chronic. You want to avoid these illnesses! Iodine will not kill cryptosporidium. Soaking that puppy in pure clorox will not kill it. You need a filter that removes everything over a certain size. Keep the clean-water parts separate from the unfiltered water parts to avoid cross-contamination.
The cartridge (the white cylinder) contains an activated charcoal filter. We have purchased a new cartridge about every 2 years (more because of concern over bacterial growth than because of reaching the 200 gallon expected life), and we backpack about 200 miles a year with two or sometimes three people. The replacement cartridges are now running about $35-$40.
The foam float can be slipped up and down the intake hose so you can force the intake sieve to rest at a water depth you want. This way you can keep the intake from resting on the bottom of a shallow stream, or you can force it to take water deeper than a pondweed covered surface.
The reviews that rate this filter as slow must be written by youngsters who can't spend 2 extra minutes at anything. If you have to filter a day's supply of water it takes a significant amount of time to get out all the bottles, assemble parts, get balanced somewhere near your water source, pre-filter (sometimes), etc etc... the actual pumping time isn't too big of a deal.
It filters down to 0.2 microns, which is small enough to exclude everything but viruses. If you are traveling overseas, you should probably upgrade filter levels to deal with viruses.
Total weight with cleaning brush and 2 ziploc bags for storage 12.4 ounces.
We did fit the output hose with a different end which can be screwed directly on to our water bottles (we use bottles with lids all the same). It's difficult to hold that multi-ringed thing that it comes with in place when you may be balanced on a slippery rock holding 3 bottles, all their caps and the filter.
It’s easy to clean... do it often... a couple of swipes with the brush after each use keeps you in good shape. If you must filter water that doesn't already look clean, pre-filter it or you will spend more time cleaning the filter. Good, clean water in the backcountry takes some patience.
Don't bother getting the SiltStopper filter which is an optional attachment. It just makes you think you can filter muddy water, and clogs constantly. Take a few coffee filters with you. If the water is really muddy let it settle in a pan for awhile first. Decant the cleanest water, pour it through the coffee filter into another pan and then filter with the Sweetwater. Carbon system filters are not meant to deal with mud. But treat it with care and it will give you good service.
easy to use, has lasted us well, we've replaced the handle unit only once, we’ve never been sick from water problems.
several parts to assemble each time you use it, I don’t like the multi-ringed part that you place over your bottle mouth at all
This is a good product that has stood the test of time, with small glitches fixed in newer models. Buy one for backpacking, and keep one in your home for emergencies.
Update On Sep 19, 2008: After all these years, our trusy filter gave out. Thankfully it was near the end of the trip, and we only had to boil water one day. We are looking at a newer technology for our next water purification system.